We're heading out to visit our Daughter in Montana, and she's having trouble with the derailleur on one of her bikes. It's an REI Mt Bike, probably at least 10 years old. Hopefully I'll get some more info, but here's a photo:



It's one of those new-fangled 'index' shifting types, If someone can shed some light on its quirks I'd be most grateful. The bike is a Novara Aspen, and she guesses it dates to ~ 2000.

Thank you!